In a mobile communication system, a radio terminal receives data (user data) transmitted from a communication destination via a radio access network (RAN). The communication destination of the radio terminal is, for example, a server or the like on the Internet. In such a data forwarding, from the viewpoint of a high-level layer equal to or higher than an IP (Internet Protocol) layer, the RAN is transparent to handling of data of the user plane (U-plane).
On the other hand, in a fifth generation (5G) mobile communication system, by increasing the RAN in sophistication, a delay time (that is, latency) of data forwarding to a radio terminal (that is, latency) is desirable to be reduced.